by Robin Schneider, Marketing Director, Green Cubes Technology
Overview
Propane powered lift trucks have long been considered a good option for indoor or mixed indoor/outdoor heavy use applications. Cleaner burning than diesel, propane provided an internal combustion engine (ICE) solution without some of the limitations of older battery technology like swapping batteries and watering. However, as motors have switched to AC power and Lithium-ion (Li-ion) batteries have become available for fast charging, the need for propane is waning. Some applications, like food, pharmaceutical or underground facilities are required to use electric forklifts and electric forklifts also have a lower cost of ownership in the long term. The change is accelerated by environmental legislation such as that from the California Air Resources Board (CARB). In this white paper, Green Cubes Technology outlines the pros and cons of propane versus modern Li-ion technology, what makes Lithium Iron Phosphate (LFP) the safest option, and how batteries can use opportunity charging to obtain similar efficiencies to propane.
About Propane Power for Lift Trucks
Propane forklifts have the power of other fossil fuel machines, and they can generally go eight hours on a cylinder without needing to their fuel recharged. For most light and medium needs, propane fueled equipment offered more power for the versus older battery technology. Unlike battery powered forklifts, the fuel is swapped out, rather than waiting for a charge. Propane lift trucks also have better drive-line torque than older electric models. Propane is clean when burned ideally, giving off mostly water vapor and carbon dioxide. It is acceptable for both indoor and outdoor work, and especially handy for situations where you need to transition between both environments.
However, propane gas is a fire hazard and can present a danger in improperly ventilated spaces and spills can also be a concern. Exposure to high levels of propane fuel occurs generally only while filling tanks or from a leak from the tank or fuel delivery system. Propane gas is heavier than air; so, leakage from a vehicle parked or stored near an unventilated pit or a lower-level room is a hazard. While exposures in small amounts are not dangerous to humans, exposures to very high concentrations of propane can produce dizziness after a few minutes of exposure. At extremely high concentrations propane acts as an asphyxiant by displacing oxygen. This fact means that a person could suffocate if exposed to high enough concentrations of propane because it dilutes the oxygen in the air.
More concerning is that incomplete combustion of propane results in the formation of carbon monoxide. Carbon monoxide and carbon dioxide are hazards when propane-powered equipment is used in enclosed, poorly ventilated areas. Symptoms of carbon monoxide and carbon dioxide overexposure include headache, fatigue, dizziness and nausea. Carbon monoxide is a toxic gas that interferes with the ability of the red blood cells to carry oxygen and exposure to high concentrations can be deadly. Because carbon dioxide is an asphyxiant gas, it can result in death in high concentrations. Life-threatening concentrations are uncommon; however, symptoms of headache, fatigue and dizziness may show that there is inadequate ventilation in the workplace. Because of these risks some jurisdictions may recommend specific ventilation rates for propane-powered forklift trucks used indoors.
Lithium SAFEFLex batteries and chargers from Green Cubes Technology
About Li-ion Power for Lift Trucks
Technology has replaced the old direct current (DC) electric motors exclusively with modern alternating current (AC) motors. Outdated DC motors were underpowered and were only able to draw power from the available battery voltage. As the battery charge reduced, so did the motor’s power output and the machine got weaker as the shift progressed. Forklifts with AC motors maintain their performance as battery voltage reduces. The operator can rely on full power throughout the shift until the voltage is so low the battery requires recharging or swapping out with a fresh one. AC motors are highly energy-efficient and their outstanding performance is boosted by advancements in battery technology. Electric-powered forklifts historically used Flooded Lead Acid (FLA) batteries. Forklift batteries are large, weighty and expensive compared to automotive batteries. More electric draw is expected to operate a heavy forklift than to start a car, and new Li-ion batteries are able to deliver high currents with an extremely flat voltage curve. Li-ion batteries can also be installed with heaters so that they can be used in a much larger range of temperature than lead acid, reducing the need for propane on this front as well. The Li-ion cell chemistry has numerous chemical variants. Lithium Iron Phosphate (LFP) chemistry is the predominant chemistry used to power MH equipment: LFP features:
- Exceptionally long cycle life (2000 - 4000 cycles to reach 80% of the original capacity)
- High power capabilities for both charge and discharge
- Lower energy/density than other Li-ion variants.
With larger industrial, motive power battery systems, space is available for the larger batteries, and weight is actually needed for the counterbalance systems. Fast charging is critical and LFP accommodating lead acid charging helps with systems safety. Cycle life and safety are prioritized. The lower voltage of LFP is a good match for Lead Acid replacement. This and the tolerance of Lead Acid charging systems make LFP the safest backward compatible option for material handling batteries. The long cycle life means an LFP battery can be installed and remain in the equipment for 8-10 years. More importantly, since LFP chemistry can accommodate high power delivered to and from the battery, a depleted LFP battery can accept a full charge in a little over one hour (i.e. 1 C rate) and it can be delivered throughout the shift when the operator has a break or lunch. Li-ion is the optimal chemistry for opportunity charging,
Evaluating the Pros & Cons of Propane VS Electric Forklifts
Propane forklift pros:
- Good for extreme temperatures or rough surfaces
- Consistent power throughout the shift
- Continuous operation: when the tank empties, simply replace with a full one
- Fuel can be available in remote locations
- Low upfront cost
Propane forklift cons:
- Non-renewable fossil fuel
- Can’t be used for certain applications
- Price fluctuations and fuel availability
- Higher long term operating costs
- Noisier than electric forklifts
- Reduced field of vision and less maneuverable
- Safety and spill risks
- Operator training
Electric forklift pros:
- Cleaner, no emissions and quiet
- Safe for food and medical applications
- Good for narrow aisle applications
- Lower cost of ownership
- Fewer moving parts
- Require less maintenance
Electric forklift cons:
- Higher upfront cost
- Most electric forklifts aren’t designed for outdoor use
- Battery charging time requirements
- Must be charged in a specific location
Learn more about Lithium SAFEFLex batteries and chargers.